Moisture control system



Dec. 27, 1938. F. c. STAMM MOISTURE CONTROL SYSTEM Filed July 17, 1955 r J M mm [AI n T N A J J m mm W a J 3 16 A k In N E .6 c A N xi M if m A A w? M W N. w 3 E Q m m\ .Q l1. 3 MN QW Q\ MM 3 x 3 mm A Patented Dec. 27, 1938 UNITED STATES PATENT OFFICE MOISTURE CONTROL SYSTEM Frederick '0. Stamm, Lockport, N. Y.

Application July 17, ,1935, Serial No. 31,776 10 Claims. (01. 34 -48) The main objects of this invention are:

First, to provide an improved moisture control system which is especially well adapted for use in the web drying apparatus of paper making machines.

Second, to provide means in a web drying apparatus for maintaining constant the moisture content of the web leaving the apparatus.

Third, to provide a web drier of the foregoing character which is very efiicient and effective for the purpose intended.

Objects relating to details and economies of my invention will appear from the description to follow. The invention is defined and pointed out in theclaims.

A structure which is a preferred embodiment of my invention is illustrated in the accompanying drawing, in which:

The single figure is a diagrammatic fragmentary view in side elevation of a moisture control system embodying features of my invention.

Referring to the drawing, l is a traveling web of paper which is arranged to pass over a series of drying cylinders, the wet end of the web being i r, at 3 and the dry end at t. The drying cylinders 2 constitute a part of a paper making machine in the illustrated embodiment, the drying apparatus being required to reduce the moisture content of the web to a predetermined constant amount.

to The drying cylinders are divided into three groupsan intermediate group 5 where most of the drying is done, a first group, 6 at the wet end of the apparatus, and a last group 1 at the dry end. The intermediate group 5 is supplied with 35 steam through a main header 8 while the first and last groups of driers are supplied with steam through headers 9 and I0 respectively.

The headers are arranged in line. as shown,

. but are separated by valves II and I2.

under pressure and is providedwith a main control or regulating valve it for controlling the steam supplied to the apparatus. A pipe 15 con- 45 ducts steam from the main supply pipe ill at the rearof the valve M to the header Ill of the last group of driers, the pipe l5 being provided with These 40 valves are normally closed. The main steam supply pipe I3 is connected to a source of steam pipe IS. The drain pipes it of the central group 5 of driers are connected to a common drain header 20 which is in turn connected to a separating receiver 2| having a steam outlet pipe 22 anda condensate outlet pipe 23. The condensate 5 outlet 23 is connected to a compound trap unit 24 having sufficient capacity to handle the condensate from section 5, the traps having an automatic air by-pass. The compound trap unit 24 is in turn connected to a pipe 25 for returning 10 the condensate to a boiler feed water heater (not shown). The steam outlet pipe 22 of the separating receiver 2i is connected to the steam header 8 of the first group 6 of driers.

The drain pipes of the drier groups 8 and 1 are 15 provided with steam traps. 26, the condensate outlets of which are connected to the drain headers 21 and 28 respectively, delivering to the pipe 25. The pipe 25, as pointed out above, returns the condensate to the boiler feed water 0 heater.

In each of thedrain pipes E9 of the central group 5 of the driers, I provide a steam restrictor 29.

Due to the fact that the restrictors cut down 26 the amount of steam which can pass through them as compared with the conventional drain pipe, the number of driers in group 6 necessary to condense the steam blown through them from group 5 is greatly reduced. This results in the 30 use of more driers in group 5, which is supplied with steam under high pressure. This increases the drying capacity of the machine andat the sametime retains the advantages of rapid. air and condensate elimination from allof the driers.

The heat transfer of the last "group 1 of the driers varies directly with the moisture in the web i'traversing thesedriers. Thus, an increase' in moisture causes an increase in" the steam fiow to these driers. I use this steam fiow to the last 40 group of driers to regulate the steam fiow to the driers in the balance of the machine so as to' efiect a constant moisture in the web leaving the machine.

' With the foregoing in} mind, I provide a control 38 comprising a first regulatortl and a second regulator 38. I The first regulator has a diaphragm 89 controlled by the steam pressure at the rear of the steam restricting orifice I! by means of a pipe 40. The second regulator has a diaphragm 4! controlled by the steam pressure in the supply pipe ill at the rear of the valve I 4 by means of a pipe 42. The regulators are differentially connected by a lever 48 pivoted to the frame of the regulator 38 at 44 and carry! ing a weight 45, the lever being pivotally connected to the regulators at 48 and 4! respectively. 7 p

The auxiliary control 36 operates the main valve H in the steam supply pipe l3 through a pipe 48 connected to a supply of air under pressure (not shown) and containing an air valve 49 connected to the regulator 38. Thus,.the control 36 acts very much like the governor of a steam turbine and varies the steam flow to the main part of the machine so as to hold the steam flow to the last group 01' driers substantially constant.

The last group I of driers is supplied with steam through the control conduitor pipe IS. The balance of the machine is supplied with steam through the main steam header or pipe It. The main valve l4 regulates the steam supply to the entire machine and is controlled by the combined action oi. the regulators 31 and 38. Orifice I! in the pipe l5 creates a pressure diflerential at this point, which differential varies with the steam flow to the last group of driers. The valve it placed in the pipe ahead of the orifice l1 keeps the pressure of the steam flowing through the orifice constant within a certain range. Thus, the only factor influencing the differential across the orifice I1 is the steam flow to the last four driers.

The controls or regulators 31 and 38 act in combination to effect the control of the main valve H. The regulator .31 being connected to the control header l5 just back of the orifice l1 reflects any change in steam flow to the last four driers and acts upon the regulator 38, causing a corresponding change in steam' pressure in the main steam header 8. However, the design of the control is such that slight changes in steam flow through the orifice I! are magnified about twenty times before reacting upon the regulator 38.

In operation, the backtender adjusts the weight 45 until the web I of paper leaving the apparatus has the desired moisture content. The control is then left alone and holds the moisture in the paper at this desired point within very close limits. As long as the various' factors aflecting the operation of the machine remain constant, the control acts to hold constant the steam pressure in the main steam header. A slight change in the stock coming to the machine will cause a slight change in moisture in the web traversing the driers. This in turn will tend to cause a slight change in the moisture of the web leaving the machine. For example, let it be supposed that this change is an increase in moisture. The increase in moisture causes an increased condensation in the last four driers with a corresponding increase in steam flow thereto, which increase in steam flow through the orifice l1 causes a drop in pressure in the pipe 40 back of the orifice. Thisdropln pressure amplified through the regulator 31 causes the regulator 38 to open the main steam valve I4 and increase the pressure in the main steam header to a point where it will offset the eflect of the regulator 31 and bring the control back to equilibrium.

Thus, a drop in pressure of only one ounce back of the orifice II will cause an increase in pressure of twenty ounces in the main steam header to bring the control back to equilibrium.

7 This increase in steam pressure in the main steam header does not aflect the operation of the last group of driers due to the automatic operation of the control valve l6. It does, however,

speed up the drying of the web I on the balance of the machineand tends to reduce the moisture in the web leaving the driers. As the web becomes drier, the demand for steam in the last four driers naturally decreases causing an increase in steam pressure back of the orifice II. This reacts through the auxiliary control 36 to reduce the pressure in the main steam header to a point where it is suificient to result in the desired moisture content of the web.

The foregoing cycle of operation is 01' course very gradual and in direct proportion to the change in moisture in the web'traversing the driers. The action is very similar to the operation of a governor on a modern steam turbine wherein a change in load may throw the main steam valve wide open in order to hold the speed constant. Thus, in my.control a slight change in moisture in the web leaving the driers will open the main steam valve to a point where the increase in drying brings the web back to the desired moisture content.

The control is always at equilibrium and neither hunts nor fluctuates. It holds the steam pressure absolutely constant in the main steam header except when called upon to change it to correspond with a slight change in moisture in the web leaving the machine.

While I have described my improvements as applied to the web drying apparatus of a paper making machine, it will be appreciated by those skilled in the art that the invention may be applied to a traveling web of any kind of material,

'such as cloth, gypsum board and paper board,

as well as paper. The control may be operated by a single drum, a multiplicity of drums, a single platen, a multiplicity oi platens, a drying chamber, a kiln, or any form of drier from which it is advisable to regulate the moisture content of the material leaving the apparatus. The number of driers in the control group may be one or any number. Further, the orifice ei'lectingthe control may be a plate orifice, an ejector, a Venturi throat or any form oi'a device which will reflect a change in steam flow by a pressure change.

When the b'acktender has once set the control,

he need give it no further attention unless it is important feature since heretofore the web was invariably too dry or too wet for five or ten minutes after a break in a conventional drier. With other driers, it was necessary for the backtender to shut the steam oil. when the web was oi! the machine. If he did not do this, the sheet was burned when it was taken back oi! the driers. If the steam was shut oil, the backtender generally waited until the paper was well over the machine before turning on the steam, with the result that wet paper went on the reel until the driers had time to come up to temperature.

With my control, the-steam is automatically reduced abouttwenty-five percent of the normal pressure carried in. the driers as soon as the sheet is of! the machine. This pressure keeps the driers warm so that the first paper of! the machine after a break is, if anything, a little on the dry side. As, the driers are gradually cooled by the web of paper, my control brings the pressure back to exactly the right point where .ssthe webisback on the driers. Thiaisavery i machine.

I have illustrated and described my improvements in an embodiment which I have found very practical. I have not attempted to illustrate.

or describe other embodiments or adaptations as it is believed this disclosure will enable those skilled in the art to embodyor adapt my improvements as may be desired.

Although I have shown and described a certain specific embodiment of my invention, I am fully aware that many modifications thereof are possible. My invention is therefore not to be restricted except insofar as is necessitated by the prior art and by the spirit of the appended claims;

Having thus described my invention, what I claim as new and desire to secure by Letters Patent, is:

1. In a moisture control system, the combination with a series of drying rolls for a traveling web of paper, the rolls being divided into groups, the heat transfer of the last group of rolls varying directly with the moisture in the web passing over the same, a main header, and individual steam headers associated with the groups of rolls, of a steam supply pipe containing a main control valve connected to the main header, a secondary pipe containing a constant pressure control valve and a restricting orifice connecting said supply pipe to the header for said last group of rolls, the steam fiow to said last group of rolls varying directly with the heat transfer thereof, and means acting to regulate said main control valve in response to the steam fiow to said last group of rolls, said means comprising a first regulator having a diaphragm controlled by the steam pressure at the side of said restricting orifice removed from said supply pipe, a second regulator having a diaphragm controlled by the steam pressure in said supply pipe, a pivoted lever differentially connecting said regulators,

and having an adjustable weight, and a control fiuid supply pipe connected to said main control valve and having a control fluid valve operatively associated with said second regulator.

2. In a moisture control system, the combination with a series of drying rolls for a traveling web, the rolls being divided into groups, the heat transfer of one group varying directly with the moisture in the web passing over the same, a

' main header, and individual steam headers associated with the groups of rolls, of a steam supply pipe containing amaincontrol valve connected to the main header, a secondary pipe containing a constant pressure control valve and a restricting orifice connecting said supply pipe to the header for said last group of rolls, the steam fiow to said last group of rolls varying directly with the heat transfer thereof, and means acting to regulate said main control valve in response to the steam fiow to said group of rolls, said means comprising a first regulator controlled by the steam pressure at the side of said restricting orifice removed from said supply pipe, a second regulator controlled by the steam pressure in said supply pipe, a pivoted lever differentially connecting said regulators and having an adjustable weight, and a control fluid supply pipe connected to said main control valve and having a control fluid valve operatively associated with said second regulator.

3. In a moisture control system, the combination with a series of drying rolls for a traveling web, the heat transfer of certain of said rolls varying directly with the moisture in the web passing over the same, of a steam supply pipe containing a main control valve, a secondary steam supply pipe containing a constant pressure control valve and a restricting orifice connecting said supply pipe to said certain rolls, the steam fiow to said certain rolls varying directly with the heat transfer thereof, and means acting to regulate said main control valve in response to the steam flow through said orifice,-said means comprising a first regulator controlled by the steam pressure at the side of said restricting orifice removed from said first named supply pipe, a second regulator controlled by the steam pressure in said main supply pipe, a pivoted lever differentially connecting paid regulators, and a control fiuid supply pipe connected to said main control valve and having a control fluid valve operatively associated with said pivoted lever.

4. In a moisture control system, the combination with a series of driers for a traveling web, said web passing in contact with the heated surface of said driers, the heat transfer of one of said driers varying with the moisturein the web passing in contact with the same, of a main steam supply pipe containing a main control valve, a secondary steam supply pipe connecting said main supply pipe to said one of said driers and containing a constant pressure control valve and a restricting orifice between said constant pressure control valve and said one of said driers, means acting to regulate said main control valve in response to pressure differential across said orifice, means communicating the regulating means with the steam in the system at opposite sides of said orifice, and means connecting the regulating means with the main control valve.

5. In a moisture control system for a traveling web, the combination with a series of driers having a heated surface traversed by the web and transferring heat to the web. the heat transfer of the last of said driers varying with the moisture'in the web traversing the same. 'and means supplying steam to all of said driers, including a steam supply connection for said last of said driers, of a main valve associated with said means for controlling the fiow of steam supplied to said driers. a steam pressure control valve in said connection for maintainingconstant the pressure of the steam supplied to said last of said driers, the steam flow tosaid last of said driers varying with the heat transfer thereof, and means acting to regulate said main valve in response to the steam fiow to said last of said driers to maintain constant the moisture in the web leaving the driers, including means in said connection between said steam pressure control valve and said last of said driers for detecting a drop or increase in pressure in the last of said driers.

6. In a moisture control system for a traveling web, the combination with a series of driers having a heated surface traversed by the web and transferring heat to the web, the heat transfer of one oi said driers varying with the moisture in the web traversing the same, and means supplying a heating medium to all of said driers. of a main valve associated with said means for controlling the flow of heating medium supplied to said driers, means for maintaining constant the pressure of the heating medium supplied to said one of said driers, the flow of heating medium to said one of said driers varying with the heat transfer thereof, and means acting to regulate said main valve in response to the flow of heating medium to said one of said driers to main tain constant the moisture in the web leaving the driers, including means between said constant pressure m taining means and said one of said driers fo detecting variations in flow of heating medium to said one of said driers caused by variations in heat transfer thereof, and means controlled by said detecting means and operatively connected to said main valve to actuate the same.

7. In a web drier, the combination of an advance drying unit and a succeeding drying'unit successively traversed by the web to be dried in heat transferring relation to the surface of the units, means for supplying steam to internally heat said advance drying unit including a regulating valve and a header for said advance unit, a connection for supplying steam to said succeeding drying unit connected to said supply means between said regulating valve and said header and provided with a pressure regulator and with an open restricting orifice between the pressure regulator and the succeeding drying unit, a pressure controlled actuating means for said regulating valve,.means for connecting said actuating means to said supply connection on the side of said orifice adjacent the succeeding drying unit and I to said steam supply means between said regulating valve and the point at which said supply connection is connected to the supply means, and means for connecting said actuating means to said regulating valve.

8. In a web drier, the combination of an advance drying unit and succeeding drying unit successively traversed by the web to be dried in heat transferring relation to the surface of the units, means for supplying steam to-internally heat said advance drying unit including a regulating valve and a header for said advance unit, a connection for supplying steam to said 5110 ceeding drying unit connected to said supply means between said regulating valve and said header and provided with a pressure regulator and an open restricting orifice between said pressure regulator and said succeeding drying unit, a

pressure controlled actuating means for said regulating valve, means for connecting said actuating means to said regulating valve, means for connecting the actuating means to said connection .at the side of the orifice adjacent the succeeding drying unit; and means for communicating the actuating means with the steam between the orifice and the regulating valve.

9. In a drier, the combination of an advance drying unit and a succeeding drying unit adapted to be heated by steam and to transfer heat to a web traversing the surface of said units, means for supplying steam to said advance drying unit including a regulating valve and a header for said advance unit, a connection for supplying steam to said succeeding drying unit connected to said supply means between said regulating valve and said header and provided with a pressure regulator for maintaining the steam pressure in said connection constant, means between said pressure regulator and said succeeding drying unit for detecting variations in fiow of steam to the succeeding drying unit, a control means for said regulating valve including a pressure actuated element, means connecting said pressure actuated element to said detecting means to be actuated by said variations in the flow of steam thereto, and means operatively connecting said control means to said regulating valve.

10. A control system for web drying machines having a main group of drying rolls successively acting upon a traveling web to be dried, a steam supply provided with a steam feed regulating valve, a drying roll spaced from said main group in the direction of travel of the web and having a steam supply connection to said steam supply between said steam feed regulating valve and said main group, a constant pressure regulating valve in said connection, an open restricting orifice between said constant pressure regulating valve and said drying roll, and pressure controlled actuating means for controlling said main valve subject to the variations in pressure in said steam connection at the side of said restricting orifice removed from said regulating valve.

FREDERICK C. STAMM. 

